Start the Season Out Right: Plant into Weed-Free Fields

Planting clean by killing all vegetation prior to planting is an important first step for weed management. Most growers take this step for granted until a control failure happens. Weeds present at planting can bind up planting equipment and prevent good seed-to-soil contact, reducing crop stand. Additionally, existing weeds will compete with crop seedlings.

 

Horseweed plants recovering following a pre-plant herbicide application. Photo Credit: Virginia Cooperative Extension

Prior to cash crop planting, growers have more options to control weeds with tillage or herbicides than in the crop. Once this opportunity is missed, options for weed control will be limited and implementation more difficult. To avoid this, make sure to follow these steps:

  1. Scout early to determine what weeds are present and what growth stage they’re in. This information will dictate which termination method will be most effective and when.
  2. Terminate when weeds are small and susceptible to the termination method.
  3. Allow adequate time for weeds to die before planting. If not completely killed, weeds may begin to recover as early as 1 week after treatment with paraquat or as long as 4 weeks after treatment with glyphosate or 2,4-D.
  4. Scout before planting to ensure all weeds are, in fact, dead and new weeds have not emerged. If further weed control is necessary, do this prior to planting.

Methods for planting clean:

  • Tillage: This tactic damages aboveground vegetation and buries weed seeds. However, this might not completely control existing weeds and can also stimulate weed seed germination.
  • Herbicides: Choice of product should be based on the weeds present. Hard-to-control weeds or cover crop species should be a major factor in this decision. Keep in mind that there might be plant-back restrictions for some herbicides depending on the cash crop.

Vegetation left on soil surface following disking. Will these plants survive? Photo Credit: Michael Flessner

Also consider a stale seedbed method. First, disturb the soil through tillage or cultivation to encourage weed seed germination. Following this flush of germination, apply another control tactic to kill these newly emerged seedlings. The process may be repeated, if desired, until crop planting. This process reduces the number of seed in the soil seedbank. The method can be time-consuming and may not affect weeds with longer periods of seed dormancy. Also, it may not control perennial weeds and could even spread these species.

 

Written by:

Kara Pittman

Michael Flessner

Victoria Ackroyd